Diagnostic tests

Specimen jar containing three female Japanese Bitterlings, 1930-1980

Doctors use tests to communicate with the patient, observe his or her body, and support their diagnosis. Many tests are now available to practitioners. They may indicate the presence of a germ or abnormal cells, or the lack or excess of certain chemicals. Genetic tests now detect disease present in the body. They even detect risk factors which indicate the likelihood of a healthy person developing a disease such as breast cancer later in life.

For instance, doctors can use three types of tests if a patient suffers from suspected stomach ulcers: stool or blood tests; endoscopes to look at the inside of the stomach; or a Breathalyser to detect Heliobacter pylori, a bacterium suspected of causing stomach ulcers. Tests can also take place outside the laboratory. Simple tests now allow women to detect pregnancy without sending urine samples to a laboratory. Expert patients measure blood sugar levels and cholesterol themselves using home testing kits.

Interpretation

However, tests are not always secure and unambiguous. Problems arise interpreting the results, or considering the risks or consequences for the patient’s treatment. For example, in a cervicalbiopsy or ’smear test’ doctors look for abnormal cells in the tissue sample taken from the female patient.

These determine whether she is at risk of cervical cancer. However, the interpretation raises questions such as when does a cell count as abnormal? And how many cells have to look different from the norm to count as significant? What does a test actually test for? Another interpretation problem arises if medical scientists disagree on the value of a test. The famous IQ tests in psychology are designed to uncover a person’s intelligence. However, some scientists doubt their value. They argue the IQ test does not reflect intelligence, only how well people can do IQ tests.

Ethical issues

Ethical issues such as immediate health risks and later consequences must be considered when using medical tests. The prenatal amniocentesis of fluid to investigate the presence of genetic disorders in the foetus carries a small risk of miscarriage. Parents and practitioner must consider this risk. What are the consequences of knowing the outcomes of a test? When does it benefit the patient to know of the presence of risk factors? Early indication of the presence of risk factors may help patients change their lifestyles. This minimises their chances of developing the condition for which they are at risk. However, knowledge of the presence of risk factors may diminish a person’s quality of life.